Method of quenching zirconium and alloys thereof

ABSTRACT

Zirconium and alloys thereof are quenched from the beta phase temperature range, i.e. at least 1,830*F., into water having a temperature of at least about 140*F., whereby to inhibit the formation of a blocky alpha structure surface layer which ordinarily forms upon subsequent heating in the alpha temperature range.

United States Patent [191 Amick 1 Nov. 12, 1974 [54] METHOD OF QUENCHING ZIRCONIUM 3,341,373 9 1967 Evans et al. 148/133 x AND ALLQYS THEREOF 3,689,324 9/1972 Wiener et a1. 148/133 X [75] Inventor: Darryl D. Amick, Albany, Oreg.

[73] Assignee: Teledyne Wah Chang Albany,

Albany, Oreg.

[22] Filed: Sept. 20, 1973 [21] Appl. No.: 399,130

[52] US. Cl. 148/20.6, 148/115 F, 148/133 [51] Int. Cl. C22f l/l8 [58] Field of Search 148/115 F, 20.6, 133

[56] References Cited UNITED STATES PATENTS 2,894,866 7/1959 Picklesimer 148/133 X Primary ExaminerC. Lovell Attorney, Agent, or Firm-Oliver D. Olson [5 7 ABSTRACT Zirconium and alloys thereof are quenched from the beta phase temperature range, i.e. at least 1,830F., into water having a temperature of at least about 140F., whereby to inhibit the formation of a blocky alpha structure surface layer which ordinarily forms upon subsequent heating in the alpha temperature range.

2 Claims, N0 Drawings METHOD OF QUENCHING ZIRCONIUM AND ALLOYS THEREOF BACKGROUND OF THE INVENTION This invention relates to the quenching of metals, and more particularly to a novel method of quenching zirconium and alloys thereof to inhibit the formation of blocky alpha structure during subsequent heating into the alpha temperature region.

It has been the practice heretofore to quench zirconium and its alloys in water of uncontrolled temperature (normally, room temperature), and thereafter to subject the material to alpha-range temperatures for the purpose of annealing and/or heating for subsequent forging or rolling. During these alpha-range heating operations, surface stresses created by the prior quenching operation result in a phenomenon referred to as critical grain growth. Large blocky alpha grains form from the surface to a depth invariably greater than 0.0050 inch, commonly reaching depths as great as 0.100 inch.

A clear distinction must be made here between this thick alpha case caused by critical grain growth, and the very thin, i.e., less than 0.005 inch alpha case commonly formed by the effect of high oxygen content in surface films. This latter type of alpha case is always removed by routine operations, such as sandblasting and pickling.

The blocky alpha structure has properties which are different from the interior of the material, and is therefore objectionable, requiring removal of the blocky alpha layer by machining, grinding, etc. The time involved in the machining and the magnitude of the loss of material resulting therefrom represent a significant cost factor in the production of usable metal.

SUMMARY OF THE INVENTION In its basic concept, this invention involves the quenching of zirconium and its alloys in water having a temperature of at least about l40F., to inhibit the formation of an alpha structure layer.

It is by virtue of the foregoing basic concept that the principal objective of this invention is achieved; namely, to overcome the aforementioned disadvantages of the prior quenching method.

The foregoing and other objects and advantages of this invention will appear from the following detailed description of the preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention zirconium and its alloys are quenched in water having a temperature of at least about l40F., The preferred water temperature is in excess of l60F., and as close to the boiling point of water as is practicable.

It is to be noted that the quenching of zirconium and its alloys cannot be carried out in most common oils, even at the elevated temperatures required for this invention, since the resulting pickup of hydrogen could adversely affect their metallurgical characteristics.

When zirconium or its alloys, for example Zircaloy IV, is quenched in accordance with the method of this invention, the formation of the previously described deleterious blocky alpha structure surface layer, which heretofore has formed during subsequent heating in the alpha temperature range, is eliminated. The prior requirement of machining off the substantial depth of blocky alpha layer thus is avoided, with consequent elimination of the excessive cost of production of usable metal resulting therefrom.

Having thus described my invention and the manner in which it may be used, I claim:

1. In a method of heat treating zirconium and its alloys by quenching from the beta phase temperature range followed by subjecting the material to an alpha range temperature treatment; wherein the improvement, comprises conducting said quenching step by immersing the material in water maintained at a tempera ture of at least about F.

2. The method of claim 1 wherein the water is maintained at a temperature of at least F.

' UNITED STATES PATENT OFFICE" CERTIFICATE OF- CORRECTION Pat ent N 3, 847,684 Dat d November 19, 1974 Darryl D. Amick I I vIr 1ve1:1tor( s) It is certified that error appears in the above-'idengified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 21', 90.0050" should read --0;050-- Signed g aisenedrh s 7th day Jamey-.191

(SEA-L) Attest: I

McCOY M. GIBSON JR. C. MARSHALL DANN Atteeting Officer C mmissi ne'If of Patents c 0.5. GOYtiNIIENT PRINTING or'nc: his (i -3N4! 

1. IN A METHOD OF HEAT TREATING ZIRCONIUM AND ITS ALLOYS BY QUENCHING FROM THE BETA PHASE TEMPERATURE RANGE FOLLOWED BY SUBJECTING THE MATERIAL TO AN ALPHA RANGE TEMPERATURE TREATMENT; WHEREIN THE IMPROVEMENT, COMPRISES CONDUCTING SAID QUENCHING STEP BY IMMERSING THE MATERIAL IN WATER MAINTAINED AT A TEMPERATURE OF AT LEAST ABOUT 140*F.
 2. The method of claim 1 wherein the water is maintained at a temperature of at least 160*F. 